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How to Learn Self-Control

A new book argues that willpower is tied directly to consumption of glucose—and we can teach ourselves new behavior. Jamie Holmes speaks to psychologist Roy Baumeister about his book, 'Willpower.'

Before she was a star musician, Amanda Palmer worked as a living statue. Standing perfectly still, she’d pose in the middle of Harvard Square, dressed as a bride, and through insults, lobbed objects, meddling drunks, and distracting jokes, she’d practice the art of nonreaction for hours on end.

“I couldn’t scratch my ear if I had an itch. If a mosquito landed on my cheek, I couldn’t swat at it,” Palmer said. “I’d get home barely alive … I would put myself into the bathtub, and my brain would be completely blank.” She credits her success as a musician in part to her time as a street performer, working in what she describes as the “ultimate Zen training ground.”

Not moving didn’t take much physical effort, it turns out, so much as it took self-control, and by not reacting, as the psychologist Roy Baumeister and New York Times columnist John Tierney explain in their instant classic, Willpower, Palmer was strengthening hers. Willpower, they argue, works like a muscle.

In 1998, Baumeister co-published a paper suggesting that self-control decisions drew on some limited resource. After resisting cookies and chocolates, he found, subjects had less self-control at a subsequent task. That finding was later extended to show that making other decisions also draws on self-control resources. In Willpower, Baumeister and Tierney convincingly describe another addendum: willpower depends on glucose as an energy source.

This last breakthrough, published in 2007, came accidentally, in a tale of academic intrigue involving Mardi Gras and a “joyless drink of glop.” By one theory, Mardi Gras allows for people to indulge their sins before Lent, and Baumeister and his fellow researchers set out to test whether pleasure might increase self-control reserves by having subjects drink ice cream milkshakes between two tasks requiring willpower.

As a control, some subjects drank a “large, tasteless concoction of low-fat dairy glop.” But the researchers found, to their initial dismay, that both the ice cream shakes and the joyless glop reversed the effects of depletion. It wasn’t pleasure that rejuvenated willpower, it was the calories, a discovery they confirmed by measuring glucose levels after self-control tasks, and, also, by comparing the effects of lemonade with sugar versus lemonade with Splenda.

This finding, as the authors detail, has impressive explanatory power. In one real-world study published earlier this year, researchers found that Israeli judges making parole decisions were likely to grant parole roughly 65 percent of the time after a meal break, but approved parole almost never right before one. Weighing parole decisions appears to consume glucose.

Some 90 percent of juvenile delinquents tested soon after being taken into custody, another study found, had below-average glucose levels. Yet another study, this one in Finland, revealed that just by looking at the glucose tolerance of convicts about to be released, researchers could predict future violent crimes with roughly 80 percent accuracy. The glucose-willpower link also sheds light on self-control problems in diabetics, hyperglycemics, and even women at that energy-scarce time of the month.

Baumeister and Tierney are primarily concerned with how this and other recent research can help people lead better lives—be better parents, stay organized, and lose weight more wisely, for instance. One chapter reveals how to compose an effective to-do list, while another explains the importance of self-awareness in planning, and how new Internet tools can help. The research is so incredibly fertile and open to new applications that even Baumeister only recently became aware of the application to poverty.

(As I’ve since tried to clarify, while the first mention of the idea I’ve seen is here, the inspiration for my recent article on the topic was drawn from a broader research agenda put forward by Harvard’s Sendhil Mullainathan and Princeton’s Eldar Shafir. By all appearances, their work was also followed up on by a then-Princeton student, Dean Spears. On the poverty front, in other words, stay tuned. Much more to come from Mullainathan and Shafir).

Dieting, as the glucose breakthrough reveals, provides an especially tricky test of willpower. As Baumeister explains it, when reached by telephone, “The catch-22 is that to diet you need willpower, for willpower you need glucose, and for glucose you need to eat. So, in a sense, you need to eat in order to have the willpower to not eat.”

Addicts wouldn’t say, as Baumeister points out, “OK, I’ll have just a little bit of cocaine every day,” but that’s essentially the strategy food addicts are stuck with. To lose weight, the authors suggest, try to make small incremental changes toward a healthier diet, and importantly, never go on a diet.

The book also tackles research into strengthening the willpower muscle without, say, taking up Amanda Palmer’s former profession. One approach has been to study the effects of breaking a habit, for example, of having subjects brush their teeth with their “wrong” hands. And, short term, consciously overriding such habitual behaviors does improve willpower strength.

Strangely, then, doing things outside of one’s comfort zone can be an end in itself, Baumeister says.

“I was in school in the 1960s, when people were rebelling against rules,” he says. “We used to complain, why do we have to stand up straight? Why do we have to follow a dress code? Now, here I am in my 50s, saying well, it turns out that there are benefits to making kids conform even to totally arbitrary rules, because teaching them to be able to change their behavior to conform to that rule builds self-control.”

Since repeated behaviors eventually turn into habits, improving willpower long term requires a unique strategy—a habit of changing habits, of continually expanding our zones of comfort.

Parents, too, he emphasized, should keep in mind that rewarding children’s self-control is a far better strategy than encouraging self-esteem. After all, as the authors note, poor self-control “correlates with just about every kind of individual trauma: losing friends, being fired, getting divorced, [and] winding up in prison.”

Willpower isn’t flawless. A few chapters drag in parts, and the authors are too dismissive of research into automatic behaviors. But the book comes close, and is sure to inspire further groundbreaking research into the mechanics of willpower. One implication is already apparent. Since repeated behaviors eventually turn into habits, improving willpower long term requires a unique strategy—a habit of changing habits, of continually expanding our zones of comfort.

One such practice, it seems, is the “routine” of learning. That’s a habit that this brilliant book will certainly nourish.

Sidebar: Do dogs depend on glucose for willpower, too?

In animal-behavior studies, researchers gauge self-awareness with what’s called the mirror test—simply, whether an animal recognizes itself in a mirror. First, they apply a small spot of odorless dye on the animal. The animal passes if, before a mirror, it touches the spot or maneuvers its body to get a better look at it. Dolphins, chimpanzees and elephants can pass the test. But dogs fail.

Here’s the wrinkle. In 2010, an experiment out of the University of Kentucky showed that not only does willpower appear to be a limited resource in dogs, but that, similar to people, dog willpower also depends on glucose. The paper was the first evidence that glucose provides the fuel for self-control in other animals.

To first deplete the dog’s self-control, researchers had the pets sit and stay in one position for 10 minutes. Afterwards, some were given a two-ounce glucose drink, while other dogs were given a sugar-free drink. Finally, the dogs were given a toy that they’d previously learned to extract food from, only this time, the toy had been altered to make removing the food impossible. Sure enough, those dogs given the sugar-free drink that had already used some self-control on sitting gave up significantly sooner when trying to extract the food.

How does this finding relate to the mirror test? Most researchers assume that self-control requires self-awareness. But whatever degree of self-awareness the mirror test gauges, its clear dogs don’t need it in order to behave themselves.